This invention relates to photo-electric coupling devices and more particularly to an improvement in the arrangement of the elements of photo-electric coupling devices for greater efficiency of manufacturing and better utilization of the light coupling between the light-emitting element and the light-responsive element.
In a typical arrangement of photo-electric coupling devices, a pair of electrodes or leads, of strip-like shape, face each other in a parallel plane relationship. Mounted on one of these leads on the surface facing the other lead is a light-emitting element, while a light-responsive element is mounted on the other lead such that the light-sensitive surface thereof faces the light-emitting element. At least two other leads are individually electrically connected to electrode portions in the opposing surfaces of the elements preferably by means of wire-bonding.
Since a certain amount of space is required for inserting the working head of a wire-bonding machine, it is impossible to perform wire-bonding while the leads carrying the individual elements are disposed in the customary final arrangement. In the conventional manufacturing procedure, therefore, it is necessary first to place the leads to receive the individual elements in positions accessible by the wire-bonding machine and then, after wire-bonding, to bend the leads individually into the final arrangement of opposing surfaces.
To obtain good photo-electric coupling efficiency, accurate positioning of these elements is required so that the positioning of the leads for wire-bonding, and repositioning of the leads, after the wire bonding, are troublesome and relatively expensive steps in manufacturing.
The typical arrangement of the light-emitting element and the light-responsive element of a photo-electric coupling device referred to, presents a further problem. A light-emitting diode (L.E.D.) is customarily utilized as the light-emitting element in a photo-electric coupling device. An L.E.D., as well-known, is a semiconductor device fabricated of alternating layers of P and N materials. Light is developed at the junctions of the juxtaposed layers and the primary light paths are outwardly through the edges of the diode and not through the major opposing surfaces of the diode.
In the conventional arrangement of a photo-electric coupling device, a major surface of the light-emitting diode is positioned opposite the light-sensitive surface of the light-responsive element. The light emitted from the edges of the L.E.D. must, therefore, be reflected by some means into the sensitive surface of the light-responsive element. In U.S. Pat. No. 4,054,801, for example, this is accomplished by making the opposing sides of the body enclosing the space between the elements arcuate and lining the surfaces of the opposing inner surfaces of the body with reflective material for focusing the light onto the light-sensitive surface of the light-responsive element.